In article 92-02-024 richard@harlqn.co.uk (Richard Brooksby) writes:>Why aren't there more editors which operate directly on the parse trees of>languages? Are there fundamental problems with this approach?

There are two problems with it.

The first is the difficulty that the moderator mentioned in the posting -
partial parsing is fairly difficult to handle. But that probably has been
beaten partially, and editors like what you suggest have been written. (An
example is the Wizard compiler for Estelle, written by NIST.)

The second is the more important one. In general, people don't want them.
Editors are the kind of program that should be very unobtrusive. The
editor shouldn't interfere with your ability to get your work done. You
sit down to program, you want to keep your thoughts focused on the
program, not on the editing process. In this context, syntax directed
editors seem to be very natural, because they take so much of the burden
of work editing away. Unfortunately, reality is slightly different - if
you have a different syntax directed editor for each language, then you're
suddenly obligated to know a collection of different editors, and you've
got to always remember which one you're using when you go to make a
change.

That's the biggest barrier - unless you want to provide an SDE which is
emacs compatible for emacs users, and vi compatible for vi users, and teco
compatible for teco users, and NeXTedit compatible for NeXTedit users, and
...